VoL1929 XLVII I HUFF,Nest and Habits ofConnecticut Warbler. 455

THE NEST AND HABITS OF THE WARBLER IN .

BY N. L. HUFF. Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 Plates XXV-XXVI.

ThE ConnecticutWarbler (Oporornisagilis) is one of the rarest of our . It was first collectedby AlexanderWilson in Connecticut,and notes concerningit were publishedin 1812.• It is seen not infrequently during migration seasons,mainly restrictedto the Mississippiriver valley in springand occasionally beyond,and to the Atlantic slopein autumn, but comparatively little is known or has been publishedof its home life and habits. For more than seventy years after the was described,its summer home was shroudedin mystery, and not until 1883 was the mystery partly cleared,when Ernest T. Seton•' discoveredthe first nest in a cold boggy tamarack swamp in Manitoba. He made no extensivestudy of the habits of the bird, and so the domesticlife of this rare songsterwas left in obscurity. Other records of its summer residenceare few, and the nest to be de- scribedin this paper is probably the first ever discoveredwithin the bounds of the , certainly the first recorded from Minnesota. 0. B. Warrens collectedyoung Connecticut Warblers in early August, 1894, in Marquette County, . Norman A. Wood4 reportsthe takingof an adult and youngon July 27, 1904, in OntonagonCounty, Michigan, and 0. M. Bryens5 reports maturebirds seen July 23, 1922, August18, 1923, and August 22, 1924, in Luce County, Michigan. These summerrecords, especiallyof immaturebirds, may be taken as goodevidence of breedingin the upper peninsulaof Michigan. It hasbeen known for manyyears that the ConnecticutWarbler is a summer resident of northern Minnesota. B.T. Gault ø saw

Amer. Ornlth., ¾, 1812. Auk, I, 1884, 192. Auk, XII, 1895, 192. Auk, XXII, 1905, 178. Auk, XLII, 1925, 451. Auk, XI¾, 1897, 222. 456 •v•, Nestand Habits of Connecticut Warbler. [Oct.Auk one and heard severalothers singing in a swampin Aitkin County on June 21, and days following,1890. Dr. Thos. S. Roberts and L. L. L6fstr6m• saw adults,one a femalewith bill full of food, on June 20, 1915,in a swampin Isanti County, and Mr. L6fstrSm

considered the bird as "a common summer resident of these Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 tamarack and sprucebogs." AlthoughI have visited the Isanti County bogs referred to, each June and July for the past five years, I have neither heard nor seen the Connecticut Warbler there, and it is bdievedthey have left the swampsof this county permanentlyfor the wilder regionsin the northern part of the State, or in . My searchfor the nest of the ConnecticutWarbler began severalyears ago, as a result of a suggestionfrom Dr. Thos. S. Roberts,whose interest, enthusiasm, and personalityhave always beena stimulusfor more intensivestudy of bird life. It was on July 13, 1925, that I made my acquaintancewith the bird in its summer home. On this date I was driving through St. Louis Countyand whilepassing a spruceswamp some miles from Tower, I heard an unfamiliar bird songcoming from the depthsof the swamp. I enteredthe swampand in a few momentshad located the tamarack tree where the singerwas perched. In spite of the fact that the tree was small and its foliage sparse,it was an hour before I was able to get an unobstructedview of the bird that enabledme to identify him definitelyas the ConnecticutWarbler. During this time he was forcedto changehis locationtwo or three times but each time he eluded his observer and concealed himself in his new station beforerenewing his song. The song of the Connecticut Warbler varies with different individuals, and at times with the same individual. The volume may be changed,and certainsyllables may be changedor omitted, but the quality of his tone is unique and practicallyinvariable, especiallyas regardstwo syllables,"freecher," always included in his song. So characteristicis his voice that one having heard him may identify him more quickly by his songthan by sight. His voiceis sharp,piercing, penetrating, rather shrillyet pleasing, and is onethat I alwaysassociate with the wild swampywilderness where he sings. As with many other it is impossibleto

Auk, XXXlI, 1915, 504. T•r Av•,VoL. XLVI. P•s•. XXV. Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021

UPPER.--NEsT ANDEoas OF CONNECTICUTWARBLER (O•orornis agilis). LOWER.--NES? SITE IN SI•HAGNUM ANY LABRADOR TEA. Vol.•929 XLVI] I I-Iul•,Nest and Habits of Connecticut Warbler. 457 expressit with words, but his most common song suggeststhe syllables,freechef-here freechef-here freechef-here freech. Occa- sionallyI have heardthe song,freechef freechef freechef, resembling somewhat that of the , but often followed by other Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 notes, and so different in quality that one would never confuse the two. Frequently only a fractional part of either song is voiced. In his summer home the ConnecticutWarbler is a shy and elusivebird, so secretivein his manner that he would rarely be seenhere, even by thoselooking for him, were it not for his be- traying song. As we near his territory we hear his clear,ringing, unmistakablevoice. Onemay easilyapproach the treefrom which he poursforth his jubilant song,for he seemsto singwith even greatervigor as we near him; but to seehim may requirea long wait, and the closestscrutiny of every part of the tree's crown. His voice has somethingof a ventriloquial quality. As one circlesslowly about the tree from which he sings,the songmay apparently comefrom the lower branches,five or six feet from the ground,while in reality the singeris situatedthirty feet or more above. He continuesto singwith vigor, but his olive greenback and yellowishunder parts blend with the leaves,and he cautious- ly keepsa branch or a small massof foliagealways between him and his would-behuman observer. The art of concealinghimself behind a relatively small obstruction,is one which he has devel- opedto a degreeapproaching perfection. Little wonderthe records of his summer life are so few. Whendriven from his song perch by too closeapproach of hisob- serverhe escapes,often unseen, from the opposite side of the tree,and the first indicationof hisdeparture maybe his jubilant, triumphant songgushing from a tree severalyards away. If one is fortunate enoughto seehim enter another tree nearby, one is impressed with the remarkablefacility with which he creeps,half hidden, throughthe tree until he reachesa secureposition, separated from his observerby a limb or a smallmass of foliage. More than once as he scamperedalong a branch,his bodylow, his headextended, seekinga suitablehiding place, I have seenhim pausean inch be- yond the covetedspot. With headand shouldersvisible he takesa hastypeep at hisobserver, then suddenly retreats a stepor two and [Auk 458 HUFF,Nest and Habitsof ConnecticutWarbler. [Oct. adjustshis positionuntil he is wholly obscured.Here, frequently on a relativelylarge branch not far from the trunk of the tree, he at oncebegins his oft repeatedsong, freecher-here freecher-here free- cher-herefreech.Whether this is a loveditty to hismate, a warning Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 to other membersof his tribe that this territory is occupied,or simplyan uncontrolledoutburst of the exuberantjoy of living, who can say? Whatever his motive, he seemsquite oblivious to the presenceof a humanobserver so long as his form is hiddenamong the branches. If one remainperfectly still or in hidingfor a while, the singer forgetsone's presence and sooner or later will moveout of hishiding place,walking along on a limb or occasionallyhopping to a nearby branch,taking some tiny insector othertidbit that meetshis fancy, all the while repeatinghis songseveral times each minute. His rel- ative inactivity, his rather slow deliberatemovements, now afford an excellentopportunity for observation. On June 6, 1926, on June 4, 1927, and again on June 3, 1928, while on botanicalexcursions through northern Minnesota, I heard or saw,on eachoccasion, Connecticut Warblers in certainswamps of Airkin County. Of theseswamps, one was selectedas the most promisingplace for observationof the habits,and the possibleloca- tion of a nest of this bird. This swampis perhapshalf or three- quartersof a mile wide and two miles or more in length. Much of its area is coveredwith a pure stand of small black spruce,some parts with an equallypure standof tamarack,but in placesthese two speciesare more or lessmixed together. The pitcher plant and the sundewthrive here, as do the buckbeanand the wild calla, the coralroot, the moccasinflower, and that rare and gorgeousor- chid, the dragon'smouth (Arethusabulbosa). In the Canadianswamp where Seton2 found the Connecticut Warbler nesting,he speaksof the songof this bird being the only noticeablesound save that of the Great CrestedFlycatcher. How differentthis Aitkin County swampl Here on a clear morningin Junethe air is filledwith bird voices. One hearsthe Hermit Thrush, the Willow Thrush, the SongSparrow and the White-throat, the Maryland Yellow-throat,BlackburnJan and PalmWarblers, four or five Flycatchers,Chickadees, Juncos, and several others, to say nothingof songsof the ScarletTanager, Rose-breasted Grosbeak, VoL1929 XLVI] ] HUFF,Nesi and Itabits of Conneciicui Warbler 459

Oven-bird,and Vireos that drift in from the bordersof the swamp. It is a placeattractive alike for the studentof plant life and the lover of birds. Recent explorations(1929) of only a part of this swamprevealed Connecticut Warblers singing in no lessthan five differentlocalities, and there are probablyseveral more than that Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 in the entire swamp. On June10, 1928,I visitedthis region for the purposeof learning more of the ConnecticutWarbler and if possiblelocating a nest. Scarcelyhad I enteredthe swamp when I wasattracted by thesong of this bird, and while observingit, anotherwas heard some150 yardsaway. The firstwas lost in a very shorttime and I advanced to locatethe secondsinger. The treefrom which he wassinging, a tamarack35 or 40 feet tall, stoodamidst the growthof smaller black spruce. The foliageof the tree wasnot denseand it seemed improbablethat any bird of his size couldlong concealhimself there,for the powerfulbinoculars revealed every twig. The song offeredconstant assurance of his presencebut the bird couldnot be seen,and after circlingabout the tree two or three times, assuredof his approximatelocation, I settleddown for a morecomplete search with the field glasses.Fully fifteenminutes had passedwhen he appeared,walking out on a branchnear the trunk of the tree,but 30 feet abovethe ground. At the baseof a nearbytree, I sat perfectly still, in a tangle of Labrador tea and soft bog . Whether he had forgottenmy presenceor merelyregarded me now as a part of the landscape,I do not know, but he no longersought to conceal himself. He oftensat motionlessfor severalminutes, except for the shakingand quiveringof his body whichalways accompanied his singing. Sometimeshe flitted abouton smallertwigs near the outer part of the crown,but most of the time he spentnear the center, walkingalong branches, deliberately searching for insects,occasion- ally snappingat one as it flew too nearhis head,but repeatinghis shortsong in a vigorousmanner, about every twelve seconds. For an hour I kept him under almostconstant observation, hoping he might givesome clue as to the whereaboutsof a nest. But not he; if he held the secret he failed to reveal it. While the growthof sprucein someparts of the swampwas so denseas to be almostimpenetrable, this placewas more open and the treeswere well spaced. A layer of sphagnumseveral inches in 460 HUFF,Nest and Habits of Connecticut Warbler [oct. depth coveredthe ground. Growingthrough this and extending from 15 to 18 inchesabove it wasa veritabletangle of Labradortea and swamplaurel, a combinationthat at timesmakes human prog- ress extremely difficult. In spite of the difficultieshowever, a thoroughsear& wasmade in the vicinity, an area extendingfrom Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 50 to 150yards in all directionsfrom the song-tree,but no evidence of a nestcould be found. At one time while the malewas singing from his usualplace, another bird washeard at a distanceof about 100 yards. The songwas differentfrom that of the male, softer and shorter,freechef, freechef, followed by severalother notes. I locatedthe bird in a smallspruce tree and identifiedit as a Con- neetieutWarbler, probablya female,since the markingswere less pronouncedthan thoseof the male I had beenwatching. Shere- peatedher songonly a few times and was then lost in a spruce thicket. Later in the day a thoroughsearch in the vicinity of this tree failedto flushany bird or givefurther indicationof a possible nest. For morethan five hours,while I remainedin the vicinity, the singingmale dung quite persistentlyto this one tree, and during this time, sofar as I wasable to observe,he left the tree only three times. Once,for a momentonly, he went to the ground,and on two otheroccasions he flitted acrossto a neighboringtree, only to return in two or threeminutes. All the whilehe repeatedhis song at short intervals, only occasionallypausing for a rest of five or ten minutes. When I moved about near his tree he always tried to concealhimself, and his songwas issued in a Thrnsh-likemanner, from a singleperch where he might remain for a long time. At other times however,his mannerwas more like that of the Vireos. He walked or flitted about the branches in a deliberate manner, industriouslygetting his meal,but alwayssinging while he worked. From several Connecticut Warblers observed before and after this one,it appearsnot uncommonfor a bird to remainin onetree for fifteen minutesor even for half an hour, but I have observednone other that dung persistentlyto the same tree for severalhours. Practicallyall have showna decidedpreference for the tam.stack, evenwhere the majority of treespresent were black spruce. Aboutthree weeks later, July 4, 1928,I wasin this swampagain for several hours, but failed to see or hear a single Connecticut Tar. A•K, VOL. XLVI. PLATE XXVI. Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021

UPPER.--]•GGS OF CONNECTICUT WARBLER. IX)WER.-•CHARACTER OF COUNTRY WHERE NEST WAS FOUND. PHOTO FROM FORESTER'SOBSERVATION TOWER. DARK BELT, BLACKSPRUCE; LIGHT BELT ABOVEIT• SMALLTAMARACKS. Vøll'9X29L¾I] I-I•r•, Nest and Habits ofConnecticut Warbler. 461

Warbler. I concludedthat either the young had left the nest and they had movedon to otherfeeding grounds, or that the maleshad ceasedtheir singing. On accountof their secretivemanner the presenceof ConnecticutWarblers in a swamp of this kind would be extremelydifficult to determine,were it not for the tell-tale Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 song of the male. On June 13, 1929, I paid another visit to this region, and at 8:30 in the morning as I entered the swamp, was greetedby the voice of a ConnecticutWarbler singingfrom a tamarack tree near the edgeof the bog. After listeningto him for a few moments! moved on toward the tree where! had observedthe singerfor sev- eral hours in 1928, a place only 300 or 400 yards away. I had coveredabout half this distanceand was wadingthrough a tangle of Labrador tea and other bog shrubsthat coveredthe groundin a little openingamong the sprucetrees. As I reachedthe centerof this openingthere was a slight flutter in the tangle at my feet. I paused,and like an arrow speedingfrom a bow, a bird with olive greenback flashedfrom the tangle and disappearedin the thicket of blackspruce. A NashvilleWarbler, I thought,from the flitting glimpseI got of the bird as sheleft the nest. I turned my eyesto the groundand there at my feet, sunken in a mossyhummock, wasan opennest with four speckledeggs, but they wereevidently not thoseof the NashvilleWarbler. From the meagerdescription ! had read of the ConnecticutWarbler's nest discovered by Seton* this might be the longsought nest. Couldit be possible?Patience, and the female bird will answerthe question. I retreated a dozen pacesand partly concealedmyself where I could seethe nest. In about ten minutesa bird appearedin the low branchesat the edgeof the openingwhere the nestwas located. Shewas aware of my presenceand evidentlyannoyed. Her actions clearly proclaimedher to be the owner of the nest. One look throughthe glassesand her identity was certain. It was a femme Connecticut Warbler. The nest had been found at lastl She dis- appearedin the thicket and I retreated to a point 20 yards from the nest. In a few momentsshe reappeared in a tree some20 feet above the groundand beyond the nest from where I sat. She was muchdistressed and calledrepeatedly in a loudmetalic tone, plink, plink, plink, but I sat like a pillar of stone. After a few moments 462 HUFF,Nest and Habits of Connecticut Warbler. [Oct.Auk she came to a tree nearly betweenme and the nest and continued her protest at my intrusion,but her note had now changedto a soft, plaintive,p-e-e-p, p-e-e-p, given in a clearflute-like tone. Like the males I had previouslyobserved, she often concealedherself among the foliage, even while sheprotested with her gentle voice. Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 On two occasionswhile in this tree, but for the moment invisible from where I sat, I heard the short song,freechef freechef freech, issuingfrom the tree, and it unquestionablycame from this female bird. After nearly half an hour of mild protest, from a height of 20 feet, shebegan to move graduallyupward in the tree. Her voice was now still, and walkingor creepingthrough the rather dense foliage, she disappearednear the top of the tree. When I had waited for about ten minuteswithout seeingor hearingher again, I decidedto leave the placefor a while to permit her to return to the nest, lest she might desertit before our evidencehad become absolutelyconclusive. As I approachedthe nest to take another look at the rare structureand eggsI was greatly surprisedto flush the motherbird againfrom the nest. As before,she darted directly into the thicketand waslost from view. Evidentlyshe had cau- tiously left the tree from the oppositeside, and at a point some distanceaway had descendedinto the tangle of Labradortea and made her way along the groundback to the nest. For two hoursI exploredthe swampand thenreturned and very cautiouslyapproached the nestingsite. At a distanceof ten feet from the nest I was able to see the bird sitting low in her deep little cup, her back well below the top of the nest, her beak and tail pointing straight upward, her white eye-ringstanding out in strongcontrast against the darkerbackground of her headand eye. I pausedto observeher, but it wasfor only a moment. Seeingme, she slippedfrom the nest, scuddinglike a mouseover the rough surfaceof bog-moss,and creepingswiftly through the tangle of low shrubs, she was fifteen feet from the nest before she left the ground. She then arose to the lower branchesof a small spruce tree, and by creepingfrom twig to twig, graduallyascended until ten or fifteen feet from the groundwhen she disappeared. Unlike the bird describedby Setona shemade no effort to enticeme away from the nest,but eachtime vanishedas quickly as possiblein the nearest cover. Vol.1020 XLVII I Hurt,Nest and Habits of Connecticut Warbler. 463

When I had taken photographsof the nestingsite and nest, I withdrew25 yards,hoping to make somefurther observationsof the femalebird. AlthoughI remainedthere for an hour shefailed to appear,nor was she at the nest. After wanderingabout the swampfor nearly two hoursI returnedbut she was not there. I Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 was away for anotherhour, but still there was no bird at the nest. In photographingthe nest, the eggshad beenleft near oneside of the little cup and I now notedthat their positionwas unchanged. Evidently the mother bird had not been at the nest for more than four hours. Had my prolongedstay in photographing,caused the shy bird to deserther nest? I fearedit had. In my own mind I was absolutelycertain of the identity of the bird I had seen,but I had no evidenceconvincing for others,that the nest and eggs were the long-soughtprize, those of the ConnecticutWarbler. When I left homeon a 300 mile tour to visit this swampI had a feelingthat somehowI shouldfind there the rare nest of this bird, and soI went preparedto bringback the evidenceof my discovery. If now the bird would only return oncemore to the nest I should havethe convincingevidence. But had I delayedtoo long? Half discouragedand half hoping,I took from my knapsacka cap- shapedhair net attachedto a wire hoopeight inchesin diameter. This I suspendedsix inchesabove the little nest. The light line suspendingthe net passedthrough a small metal ring four feet abovethe groundand directly over the nest, and was then attached to a tree 25 yardsaway. A light weightattached to the line just below the metal ring and securedin a mannerto prevent it from droppingto the nest, insuredquick actionwhen the line was re- leased. I wentfor anothertour of the swamp. I had little hopethat the mother bird would return to the nest after an absence of five or six hours. As I wanderedabout the swampmy anxiety for the contentsof the nest was constantlyincreasing, for I couM not but contemplatewhat wouldhappen if a red squirrelthat friskedabout within ten feet of the nest while ! watched,should find the eggs beforemy return. An hour and a half passedand at 5:30 in the afternoonI returned,cautiously approached the tree25 yardsfrom thenest and released the line suspending the net. The net dropped. I rushed toward the nest, lest if the bird were there she should [Auk 464 Nestand Habitsof ConnecticutWarbler. toot. break the net or strugglethrough it before I reachedher. I half hopedto seea bird flutteringin the net. At ten feet from the nest I paused. Alas, alas! There lay the net neatly spreadupon the mossabove the nest, but no flutteringbird. With disappointed eyesI gazedinto the nest. What! A beak and tail pointingup- Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 ward, a white eye-ring,just as I had seenthem earlier in the dayI Can it be possible?I started to rub my eyes,but just then there was a commotionin the nest; there was a bird fluttering in the net and it was the ConnecticutWarbler! So fine and light was the net and so gently had it fallen uponthe soft mossthat the sitting bird had not been disturbed, and made no effort to leave until I approachedto within eight or ten feet of her nest. I now had the nest, the eggs,the bird, and the evidencewas complete. The spotchosen for the nestingsite was a little openingamong the black sprucetrees, not more than 30 yards from the marginof the swamp. A luxuriantgrowth of sphagnumcovered the ground everywhereto a depth of severalinches. The nest was a rather deep,rounded cup, compactand well made. Inside it measured aninch and a halfin depth,and two inches in width. Thewall of the nest was approximatelyhalf an inch in thickness,and was composedentirely of fine dry grasses,except for a few black plant fibersresembling horse hairs, woveninto the lining of the bottom. It was sunkenin a mossymound, the top of the nest being level with the top of the moss. Labradortea and swamplaurel, low bog shrubsthat formeda densetangle throughoutthe little opening, overtoppedthe mossby a foot or moreand offeredample protec- tion for the otherwiseopen nest. The eggs,four in number, were of a delicate pinkish white, marked with brownishdots and splotches,which varied in color from very pale tints throughthe darkershades of purplishbrown, someof the larger onesbeing so dark as to appear almost black. The markingswere much heavieron the large end, gradually di- minishingin sizeand numberstoward the small end. In one case the whole of the smallerend was almost entirely white. In length the four eggsvaried, measuringin inches.78, .St, .St, and .84 respectively.They wereof uniformwidth, .56, givingan average sizeof .81 x .56 for the dutch. The sizeof the eggsdiscovered by Seton • was .75 x .56. Vol.1929 XL¾I1 I H•rr, Nestand Habits oy Connecticut Warbler. 465

The identificationof the 'bird was confirmed by Dr. Thos.S. Roberts,Director of the Museumof Natural History, University of Minnesota, and the nest, eggs,and mother bird have been de- positedin the Museum. Departmentof Botany, Downloaded from https://academic.oup.com/auk/article/46/4/455/5256472 by guest on 30 September 2021 Universityof Minnesota, Minneapolis,Minnesota.